On Fri, 24 Oct 2014 16:38:40 -0700 [off-list ref] wrote:

Hello all,

I was converting from a 2 disk raid1 array to a 4 disk raid5 (3+1s) in preparation to convert to a four disk raid6. I added the two additional component devices and did a:
Mdadm --grow /dev/md1 --level 5 --raid-devices 3

I guess you mean "to a 3 disk raid5 (2+1s)" ...

And off it went. I had a power failure a good ways in and now when the system boots, it runs the array, attempts to restart the reshape then disk IO locks up hard.

I figure it is disk IO rather than a complete system lockup as I have about 10 seconds of interactive shell before it locks. If I enter a dmesg command then that command will succeed. After the lockup, subsequent dmesg commands succeed (dmesg is in cache) but another command such as ls will lock up. Cat /proc/mdstat shows the reshape in progress but it doesn't actually progress beyond the point at which the system locks.

Booting from a USB stick, I tried:
Mdadm --assemble --readonly
But that too hangs the system.

Do I have any recourse beyond just recreating the array and restoring from backup? Kernel is 3.16.

Probably it can be fixed...

Can you include the output of "mdadm -D" instead of just mentioning the
command :-)
Also "mdadm --examine" of each device.
And "mdadm --version".

And
   cat /proc/PID/stack
for and PID which is in "D" state in 'ps'.

NeilBrown